A driver state monitoring (DSM) system includes a wearable device main body worn by a user, a display unit, and an information collection unit that collects information related to a body state of the user. The DSM system includes a controller that, based on the collected information, senses a situation associated with the user's body state, and converts the collected information into a numerical value representing the body state of the user in context of the sensed situation. The controller further calculates a well-driving score for the user based on the numerical value that represents the body state of the user in context of the sensed situation； and controls at least one of the display unit or an image information output device to display the well-driving score and the numerical value that represents the body state of the user in context of the sensed situation.
